24 
FROM THE PIMAS VILLAGES TO THE RIO GRANDE. 
and valley; but these being, in this case, so intimately connected, ■we will give the whole 
district the name of the most prominent, the Playa de los Pimas. The term playa is given to 
the beds of these small basins or depressions, which receive the drainage from the surrounding 
slopes. During the season of rain, the surface waters are collected and spread over a broad 
level area, soon to be absorbed and evaporated, leaving the beds smooth, and to be baked hard 
by the mid-day sun of the dry season. These playas are often called lagunos, dry lakes, salt 
lakes, &c., depending solely upon the time or season of the traveller’s visit. 
The Playa de los Pimas, the largest encountered during our examinations, is immediately to 
the west of the Dos Cabezas, or northern end of the Chiricahui mountains, and covers an area 
of about sixty square miles. Its surface was, when crossed February 28, 1854, and also 
July 30, 1855, hard and smooth, and apparently as level as a frozen lake. In fact, the effect 
in crossing, excepting in point of temperature, was very analogous to that experienced in 
crossing a broad, smooth field of ice. Not a particle of vegetation is found upon its surface, 
which is entirely free from dust, and so hard that our mules and heavily laden wagons scarcely 
made an impression upon it. It is bounded by smooth and grassy plains, sloping back to the 
bases of the mountains. 
To the northwest of the Playa the plain slopes up to a scarcely perceptible summit, beyond 
which the waters between Mount Graham and the Calitro Mountains, forming the Aravaypa 
Creek, are drawn off thirty miles parallel to these mountains, and then meeting an obstacle 
to its continuous progress to the Gila, turns westward, and by a short canon through the Calitro 
Mountains enters the valley of the San Pedro, twelve miles above its mouth, presenting thus, in 
a small scale, the same striking features as the Upper Gila. 
The Rio San Pedro, a tributary of the Gila, the western limit of the 2d section, heads in 
the plateau in which the Yaqui and other rivers of the Gulf of California take their origin, 
and trends off one hundred and twenty-six miles to the northwest, draining a valley or trough 
lying between parallel ranges, the average width of which is about fifteen miles, the alluvial 
bottom being about three-quarters of a mile wide. 
Col. Cooke, in 1846, struck this stream near its source, and followed down its valley, with a 
train of wagons, fifty-five miles to the Tres Alamos, and there turned westward, following a 
trail leading through a break in the mountains to Tucson. 
At the Tres Alamos, the valley is open, broad, and smooth, bounded by low terraces, which 
slope back to the bases of tbe mountains. The valley continues open, down to a point opposite 
the southern end of the Santa Catarina Mountains, (Colorado Peak,) where the foot spurs of this 
mountain bluff down, meeting the terraces on the right bank from the Calitro Mountain, and 
changing the direction of the valley for a short distance, reduces it to a gorge. Below this 
gorge, the valley alternately widens and narrows to its junction with the Gila, leaving beautiful 
oval meadows, separated by short stretches of bottom land, which have been narrowed down 
to a few hundred yards by the bluffs of the impinging spurs. 
These meadows are grassy and inviting, and bounded by terraces, the foot slopes of the ad¬ 
jacent ridges, ranging from twenty to one hundred feet in altitude. These terraces are sparsely 
covered with a growth of grama grass, cereus, and larrea, and the surfaces are generally 
smooth, forming, in extension, continuous and uniform slopes, but at the same time are much 
cut up by deep drains and washes, ramifying like the woody fibres of a leaf. 
• The valley bottom is generally smooth and open, with the stream bed curving through it, 
sometimes a few inches, and at others as much as fifteen feet below the surface of the meadow. 
